Food allergies may be outgrown only to become more serious

Children who outgrow one type of food allergy may go on to develop a more serious allergy to the same food, according to a new study.

The research, presented at the annual meeting of the American Academy of Allergy, Asthma & Immunology (AAAAI) in San Diego this week, analysed data from 1,375 children who attended The Children's Hospital of Philadelphia (CHOP) from 2000 to 2012, of whom 425 were shown to have an allergy to a particular food – most commonly soy, wheat, egg, or milk.

Seventeen of those had developed EoE (eosinophilic esophagitis), a more severe form of allergy that has been on the rise in recent years, after an initial allergy to the food had resolved.

The study’s authors, led by paediatric allergist at CHOP Jonathan Spergel, suggest that food allergic children should be monitored closely for signs of EoE.

"The pattern we found in those 17 patients suggests that the two types of food allergy have distinct pathophysiologies—they operate by different mechanisms and cause different functional changes," said Spergel. "However, this pattern also raises the possibility that prior IgE-mediated food allergy may predispose a patient to developing EoE to the same food."

"These two types of allergy have some elements in common, but patients with EoE usually don't go on to develop tolerance to the foods that trigger EoE," he said.

EoE is characterised by painful swelling of the oesophagus and difficulty swallowing and can occur in both children and adults. IgE-mediated food allergy can result in a range of adverse immune responses, from the mild to the severe.

The researchers also suggested that desensitisation therapy for food allergies, in which patients are given tiny quantities of the allergen in an effort to build tolerance, may trigger EoE in about 10% of those undergoing treatment – something for healthcare providers to bear in mind.

Food manufacturers must label 14 allergens under EU law – peanuts, tree nuts, soybeans, mustard, eggs, lupin, milk, fish, cereals containing gluten, sesame, celery, sulphur dioxide, molluscs and crustaceans. For products that do not intentionally contain these as ingredients, current industry best practice is simply to take all necessary precautions to avoid cross contamination and flag up the possibility of allergens' unintentional presence.